Toroidal rotation braking with<i>n</i>= 1 magnetic perturbation field on JET

Sun, Youwen; Liang, Y.; Koslowski, H. R.; Jachmich, S.; Alfier, A.; Asunta, O.; Corrigan, G.; Giroud, C.; Gryaznevich, M.; Harting, D.; Hender, T. C.; Nardon, E.; Naulin, V.; Parail, V.; Tala, T.; Wiegmann, C.; Wiesen, S.; Contributors, Jet‐Efda

doi:10.1088/0741-3335/52/10/105007

Cited by 74 publications

(94 citation statements)

References 28 publications

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“…A detail comparison of T EFCC profile induced by the n = 1 field between the experimental observation and calculation based on neoclassical toroidal viscosity (NTV) theory [11] has been investigated [12]. The NTV torque profile calculated in the ν regime including the boundary layer effect agrees well with the measured one.…”

Section: Plasma Rotation Brakingmentioning

confidence: 52%

Overview of ELM Control by Low n Magnetic Perturbations on JET

Liang

Koslowski

Jachmich

et al. 2010

Plasma and Fusion Research

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A series of ELM control experiments have been performed on JET aiming at a better understanding of the plasma response to applied magnetic perturbations. The dynamics of the edge profiles with applied n = 1 fields have been studied in the type-I ELM H-mode plasmas. Typically, the pedestal density decreased by about 20 % when the n = 1 perturbation field was applied (So called pump-out effect). However, there is no influence of the n = 1 fields on the recovery rate of the pedestal pressure, but the ELM crash occurs earlier and at a lower level of the pedestal pressure and pressure gradient. The compensation of the density pump-out has been demonstrated using either gas fuelling or pellets injection in low triangularity H-mode plasmas. Strong toroidal rotation braking by more than 60 % has been observed, and found to be independent on the safety factor. The calculated Neoclassical Toroidal Viscosity (NTV) torque profile in the ν regime including the boundary effect is in agreement with the observed torque profile induced by the n = 1 fields on JET. No complete ELM suppression was observed by application of either n = 1 or n = 2 fields with a Chirikov parameter above one at √ Ψ ≥ 0.925, which is one of the important criteria for the design of ITER ELM control coils.

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Section: Plasma Rotation Brakingmentioning

confidence: 52%

Overview of ELM Control by Low n Magnetic Perturbations on JET

Liang

Koslowski

Jachmich

et al. 2010

Plasma and Fusion Research

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“…Strong magnetic braking effect without mode locking during the application of NAMP has been observed in the experiments in tokamaks [12][13][14][15]. The NTV torque is a good candidate to explain the observed braking effect.…”

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confidence: 74%

“…Here, is the collisionality. The typical collisionality regime on DIII-D [13] and JET [15] are close to the transition of 1= and À ffiffiffi p regimes. Furthermore, particles with different energy are in different collisionality regimes.…”

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confidence: 96%

Neoclassical Toroidal Plasma Viscosity Torque in Collisionless Regimes in Tokamaks

et al. 2010

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Bumpiness in a magnetic field enhances the magnitude of the plasma viscosity and increases the rate of the plasma flow damping. A general solution of the neoclassical toroidal plasma viscosity (NTV) torque induced by nonaxisymmetric magnetic perturbation (NAMP) in the collisionless regimes in tokamaks is obtained in this Letter. The plasma angular momentum can be strongly changed, when there is a small deviation of the toroidal symmetry caused by a NAMP of the order of 0.1% of the toroidal field strength. It is known that the magnetic fields used in confining plasmas are usually spatially nonuniform or bumpy. The bumpiness of the fields increases the plasma viscosity and consequently the rate of the plasma flow damping. When the collision frequency is smaller than the bounce or transit frequency of the particles that traverse through the bumpiness of the fields, particles experience the resistance of the field when they either reflect back or slow down by the fields. This resistance enhances the plasma viscosity. The underlying physics can occur in any magnetized plasmas confined by the spatially nonuniform fields.The magnetic field of a tokamak is designed to be toroidally symmetric. Realistically, there is always a slight nonaxisymmetric magnetic perturbation (NAMP) due to an intrinsic error field, magnetohydrodynamics (MHD) perturbations in the plasma and external magnetic perturbation applied to control edge localized modes (ELMs) [1,2] and resistive wall modes (RWMs) [3]. In stellarators, the plasma diffusion in collisionless regimes induced by the helical magnetic field has been developed since the 1960s [4]. The neoclassical viscosity can also be obtained by solving the drift kinetic equation numerically [5]. However, the ordering of the NAMP in tokamaks is different from that in stellarators. In the last few years, the neoclassical toroidal plasma viscosity (NTV) theory in different asymptotic limits of the collisionless regimes [6][7][8][9][10][11] has been developed to describe the plasma momentum dissipation induced by the NAMP field in tokamaks.The importance of the NTV torque in momentum confinement has been highlighted by the most recent experimental observations. Strong magnetic braking effect without mode locking during the application of NAMP has been observed in the experiments in tokamaks [12][13][14][15]. The NTV torque is a good candidate to explain the observed braking effect.The experimental regime in present tokamaks as well as the International Thermonuclear Experimental Reactor (ITER) [16] covers both the 1= and À ffiffiffi p regimes and their transitions. Here, is the collisionality. The typical collisionality regime on DIII-D [13] and JET [15] are close to the transition of 1= and À ffiffiffi p regimes. Furthermore, particles with different energy are in different collisionality regimes. In order to model the toroidal plasma rotation with NAMP and compare it with the observation, we need to know the exact NTV solution in the transition regimes, as well as in the asymptotic limits of t...

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“…Since in previous analyses some have reported agreement between the observation of rotation damping with the estimation of NTV from analytic theory [5] while the others have shown a difference [7], it is important to verify the NTV calculation methods before applying them to experiments. The present result encourages us to use the combined analytic formula to evaluate and analyze NTV in experiments.…”

mentioning

confidence: 99%

“…The radial transport is not intrinsically ambipolar and is called nonambipolar transport in general, and the toroidal torque in tokamaks is particularly called neoclassical toroidal viscosity (NTV) torque. The NTV torque has been observed and studied in many tokamaks [5][6][7], since the change of rotations is apparent when a small nonaxisymmetric perturbation is applied. However, theoretical predictions are nontrivial due to different particle orbits, precessions, and collisions.…”

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confidence: 99%

Neoclassical Toroidal Viscosity Calculations in Tokamaks Using aδfMonte Carlo Simulation and Their Verifications

et al. 2011

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Neoclassical toroidal viscosities (NTVs) in tokamaks are investigated using a δf Monte Carlo simulation, and are successfully verified with a combined analytic theory over a wide range of collisionality. A Monte Carlo simulation has been required in the study of NTV since the complexities in guiding-center orbits of particles and their collisions cannot be fully investigated by any means of analytic theories alone. Results yielded the details of the complex NTV dependency on particle precessions and collisions, which were predicted roughly in a combined analytic theory. Both numerical and analytic methods can be utilized and extended based on these successful verifications.

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Toroidal rotation braking withn= 1 magnetic perturbation field on JET

Cited by 74 publications

References 28 publications

Overview of ELM Control by Low n Magnetic Perturbations on JET

Overview of ELM Control by Low n Magnetic Perturbations on JET

Neoclassical Toroidal Plasma Viscosity Torque in Collisionless Regimes in Tokamaks

Neoclassical Toroidal Viscosity Calculations in Tokamaks Using aδfMonte Carlo Simulation and Their Verifications

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